glPolygonOffset(3G)	       OpenGL Reference		   glPolygonOffset(3G)

NAME    [Toc]    [Back]

     glPolygonOffset - set the scale and units used to calculate depth values

C SPECIFICATION    [Toc]    [Back]

     void glPolygonOffset( GLfloat factor,
			   GLfloat units )

PARAMETERS    [Toc]    [Back]

     factor  Specifies a scale factor that is used to create a variable	depth
	     offset for	each polygon. The initial value	is 0.

     units   Is	multiplied by an implementation-specific value to create a
	     constant depth offset. The	initial	value is 0.

DESCRIPTION    [Toc]    [Back]

     When GL_POLYGON_OFFSET_FILL, GL_POLYGON_OFFSET_LINE, or
     GL_POLYGON_OFFSET_POINT is	enabled, each fragment's depth value will be
     offset after it is	interpolated from the depth values of the appropriate
     vertices.	The value of the offset	is factor * DZ	+  r * units, where
     DZ	 is a measurement of the change	in depth relative to the screen	area
     of	the polygon, and r is the smallest value that is guaranteed to produce
     a resolvable offset for a given implementation.  The offset is added
     before the	depth test is performed	and before the value is	written	into
     the depth buffer.

     glPolygonOffset is	useful for rendering hidden-line images, for applying
     decals to surfaces, and for rendering solids with highlighted edges.

NOTES    [Toc]    [Back]

     glPolygonOffset is	available only if the GL version is 1.1	or greater.

     glPolygonOffset has no effect on depth coordinates	placed in the feedback
     buffer.

     glPolygonOffset has no effect on selection.

ERRORS    [Toc]    [Back]

     GL_INVALID_OPERATION is generated if glPolygonOffset is executed between
     the execution of glBegin and the corresponding execution of glEnd.














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glPolygonOffset(3G)	       OpenGL Reference		   glPolygonOffset(3G)

ASSOCIATED GETS    [Toc]    [Back]

     glIsEnabled with argument GL_POLYGON_OFFSET_FILL, GL_POLYGON_OFFSET_LINE,
     or	GL_POLYGON_OFFSET_POINT.

     glGet with	argument GL_POLYGON_OFFSET_FACTOR or GL_POLYGON_OFFSET_UNITS.


MACHINE	DEPENDENCIES
     GL_POLYGON_OFFSET_LINE and	GL_POLYGON_OFFSET_POINT	are not	implemented on
     XS, XZ, Elan, and Extreme,	RealityEngine, RealityEngine2, and VTX and
     InfiniteReality systems.

SEE ALSO    [Toc]    [Back]

     glDepthFunc, glDisable, glEnable, glGet, glIsEnabled, glLineWidth,
     glStencilOp, glTexEnv


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